https://celsiuscity.eu/wp-content/uploads/2020/06/Waste-heat... pages 7-9
The purpose built machines for mining (ASICs) turn electrical energy into heat through performing hashes. If you need electrical heating there's functionally no difference between turning a regular heater on or turning on an ASIC. The benefit of turning an ASIC on instead is you can recoup some of the cost of expending the electricity.
If your house is one of the few that have an electric furnace, there’s no difference. For most people, though, there’s a huge difference. Running an appliance such as a computer to heat a house will cost more and be worse for the environment.
It’s true this is as good as resistive heating in terms of heating efficiency, but it is still far less efficient than a heat pump. Unless you are in an area with a large excess of renewable energy it probably doesn’t make sense environmentally to use an asic heater.
It looks like the same company still makes some products that leverage waste heat from computation (https://qalway.com/fr), just not ones that specifically mention crypto as the source of the computation.
Source: https://www.aboutamazon.com/news/sustainability/the-super-ef...